翻譯名義集 3.120

3.120

[Gaṅgā] Translated here as Coming from Heaven, because it is seen descending from a high place. Also said to be the name of the river goddess, taken as the name of the river. The Record of the Western Regions says: 'Formerly called Mount Heng or Heng sands, which are errors.' Zhang'an says: 'The sūtras often take the sands of the Gaṅgā River as a measure for four reasons: first, most people recognize it; second, those who enter it gain merit; third, it is the greatest among the eight rivers; fourth, it is the birthplace of the Buddha. These correspond to the four siddhāntas.'